1,2-dithiolium compounds as corrosion inhibitors

ABSTRACT

1,2-dithiolium compounds are prepared by oxidizing 1,2-dithiole3-thiones. In general, aliphatic-substituted dithiolium compounds have been found to be more stable and more water-soluble than aryl-substituted dithiolium compounds. Dithiolium compounds are useful as corrosion inhibitors in aqueous and/or aerated and/or acidic systems. Their usefulness as corrosion inhibitors is enhanced by the high water solubility and stability of the aliphatic-substituted dithiolium compounds.

ilnite States Patent 1191 Oude Alink 1 Feb. 12., 1974 1,2-DITHIOLIUM COMPOUNDS AS CORROSION lNl-llBlTORS [75] Inventor: Bernardus A. Oude Alink, St. Louis,

[73] Assignee: Petrolite Corporation, Wilmington,

Del. 7

[22] Filed: June 22, 1972 [21] Appl. No.: 265,243

Related [1.8. Application Data [62] Division of Ser, No. 79,709, Oct. 9, 1970.

[52] US. Cl. 21/2.5 R, 21/27 R, 134/3,

134/41, 252/855 E, 252/395 [51] Int. Cl. C23f ll/04, C23f 11/16 [58] Field of Search 21/2.7 R, 25R; 252/395 [56] References Cited UNITED STATES PATENTS 2,912,386 ll/l959 Salzberg 252/395 Primary Examiner-Barry S. Richman Attorney, Agent, or Firm-Sidney B. Ring [57] ABSTRACT 1,2-dithiolium compounds are prepared by oxidizing 1,2-dithiole-3-thiones. In general, aliphatic-substituted dithiolium compounds have been found to be more stable and more water-soluble than aryl-substituted dithiolium compounds. Dithiolium compounds are useful as corrosion inhibitors in aqueous and/or aerated and/or acidic systems. Their usefulness as corrosion inhibitors is enhanced by the high water solubility and stability of the aliphatic-substituted dithiolium compounds.

18 Claims, No Drawings 1,2-DITIIIOLIUM COMPOUNDS AS CORROSION INHIBITORS Divison of Ser. No. 79,709 Filed Oct. 9, I970.

This invention relates to l,2-dithiolium compounds and most preferably aliphatic-substituted dithiolium compounds; and to uses thereof particularly as corrosion inhibitors in aqueous and/or aerated and/or acidic systems.

1,2-dithiole-3-thiones are known compounds prepared by a variety of methods. Examples of such compounds, and methods for their preparation, are disclosed in THE CHEMISTRY OF HETEROCYCLIC COMPOUNDS, Multi-Sulfur and Sulfur and Oxygen Five-and Six-Membered Heterocycles, PART 1, pages 237 386, by David S. Breslow et a l., lnterscience Publishers, 1966.

1,2-dithiole-3-thiones may be expressed by the formula:

where R and R are substituted groups, for example, alkyl, aryl, cycloalkyl, alkenyl, alkynyl, alkaryl, aralkyl, heterocyclic, etc. In addition, one of the above Rs may be hydrogen. Examples of a wide variety of 1,2- dithiole-3-thiones are presented in the above text by Breslow et al in Table 4, pages 352 366, which is incorporated into this application as if part hereof.

1,2-dithiole-3-thiones are conveniently prepared by the classic method of reacting an olefin with sulfur, for example, according to the following equation:

The olefin employed in the reaction contains 1. a reactive double bond 2. a primary carbon atom 3. at least four hydrogen atoms on the 3 terminal carbons with at least one hydrogen on the carbon beta to primary carbon atom.

This reaction is carried out at any suitable temperature and time, for example, at about 100 to 300C, such as from about 140 to 240C. but preferably from about 160 to 220C. for a period of about 2 to 160 hours, and about to 50 hours, but preferably about to 40 hours.

The following examples are presented by way ofillus- IltlliOfl and not of limitation to show the preparation of l.2-dlthiule-3-thlones which may be employed as starting materials to prepare the dithiolium compounds of this invention- EXAMPLE 1A temperature. The product was collected and crystallized from benzene, red crystals, (32 grams, 50 percent yield), m.p. l22l24C.

EXAMPLE 2A Preparation of 4-(3-methoxy-4-hydroxy)phenyl-l,2-.

dithiole-3-thione In a suitable reactor equipped with a stirrer, thermometer, addition funnel and reflux condenser was placed, 32 g of sulfur, 1.0 g of di-otolylguanidine as catalyst and cc of mesitylene as solvent. The mixture was brought to a reflux (170C.) and over a 1 hour period 66 g of isoeugenol was added dropwise. Reflux was continued for 48 more hours. The mesitylene was decanted from the solid. The solid was treated twice with 500 cc portion of a 5 percent aqueous potassium hydroxide solution. Upon acidification the product precipitated as a brown solid.

EXAMPLE 3A Heating at 210215C. was continued for an additional 14 hours. The product was distilled and there was collected 220 g of 4-neopentyl-5-t-butyl-l,2- dithiole-3-thione, b.p. l85C. (3-4 mm Hg).

(CHa)a|C \S (CH )aCCHz(ll=S V EXAMPLE 4A Preparation of 4,5-tetramethylene-l,2-dithiole-3- thione In a suitable reactor equipped with a stirrer, reflux condenser, thermometer and addition funnel was placed 24 g. ofsulfur, 171 g of carbon disulfide and 150 cc of dimethyl formamide. The mixture was cooled to 0C. and under continuous stirring and cooling 132 g. of l-morpholino-l-cyclohexene was introduced over a k hour period. After the addition was completed, stirring was continued for an additional 16 hrs. The resulting slurry was poured into water and the resulting orange solid crystallized from acetone, m.p.'9597C. Yield 37 percent.

The following Table presents illustrative 1,2-dithiole- 3-thiones of the formula The radical indicated replaces the-Hs th positions as indicated.

\OOOQQUI-PLAN TABLE I CH3 CH:

in the 4th and/or 4-CH -5-(2-thienyl) 4-(5-CH -2-thienyl-)-5-CH 4-CH -5-(5-CH -2-thienyl) 1,2-thiole-3-thiones can be converted to 1,2- dithiolium compounds by oxidizing 1,2-dithiole-3- thiones. Any convenient method of oxidation can be employed I have found that the preferred method of preparation depends on the particular thione to be oxidized. For example, where the thione yields an unstable dithiolium compound, it is desirable to precipitate the dithiolium salt from solution so that it does not decompose. This is done by precipitating the thiolium as an insoluble salt so it will not be decomposed by further oxidation. For example, aryl thiones when converted to the corresponding dithiolium compounds are unstable to further oxidation but their decomposition can be prevented by precipitation from solution during oxidation as insoluble salts.

l have now discovered that non-aryl substituted, such as aliphatic, dithiole-thiones when converted to the corresponding dithiolium compounds yield stable compounds which are not subject to further oxidative decomposition. Therefore, it is not as important to precipitate such dithiolium compounds from solution as insoluble salts.

I have further discovered that, in general, the aliphatic dithiolium compounds are also more water soluble than the aryl dithiolium compounds. For example, certain aliphatic dithiolium compounds are at least percent water soluble in contrast to the less than 10 percent solubility of the aryl dithiolium compounds. Thus aliphatic dithiolium compounds are not only more soluble but are also more stable than the aryl compounds.

I have further discovered that because of their high aqueous solubility and stability the aliphatic dithiolium compounds are particularly useful as corrosion inhibitors in aqueous and/or aerated and/or acidic systems.

A wide variety of oxidizing agents can be employed, as illustrated by the following:

1. aqueous solution of hydrogen peroxide 1 2. hydrogen peroxide and an organic or inorganic acid barium permanganate t-butyl-hydroperoxide m-chloroperbenzoic acid Caros acid pe'racetic acid potassium persulfate chromic anhydride 10. perchloric acid, etc.

11. other oxidation agents can also be employed.

The choice of oxidizing agent will depend on the particular thione to be oxidized, economics, etc.

In general, the thione is oxidized in a suitable solvent at as low a temperature consistent with a reasonable reaction time so as to minimize side reactions. The particular reaction time will depend on the particular thione, the particular oxidizing agent, etc.

In practice reaction times of from 0.5 hours to 24 or more hours are employed; with hydrogen peroxides shorter time can be employed such as from about 1 2 hours. With milder oxidizing agents such as organic peroxides longer times may be employed such as 24 hours with chloroperbenzoic acid.

Any solvent that does not interfer with the reactants and products can be employed for example; water, methanol, ethanol, l-propanol, butanol, acetone, dimethyl sulfamide, dimethyl formamide, ether tetrahydrofuran, chloroform, carbon tetrachloride, etc.

In general, room temperature or lower is preferably employed to reduce side reactions. Higher temperatures may be employed in oxidizing certain thiones such as about 50C. or higher in certain instances.

Although I have illustrated this invention with the oxidation of thiones, dithiolium compounds can be prepared by other methods such as for example by those described in Advances in Hetcrocyclic Chemistry" Katritzby, ct al., Vol. 7, 1966, published by Academic Press, pp 39-151, which is incorporated herein as if part hereof.

The following Examples are presented by way of i1- lustration and not of limitation.

EXAMPLE 1 3-t-Butyl-4-neopentyl-1,2-dithiolium hydrogen sulfate.

In a 2 liter four necked round-bottom flask equipped with a mechanical stirrer, a thermometer, a reflux condenser and an addition funnel was placed a mixture of 260 grams of 4--neopentyl-5-t-buty1 1,2-dithiole-3- thione and 500 cc of glacial acetic acid. The mixture was cooled to 15C. and 258 grams of 30 percent hydrogen peroxide was added at such a rate that a reaction temperature of 1525C. was maintained (two hours). After the addition was completed, the mixture was stirred for an additional 2 hours at room temperature. The solvents were distilled off under diminished pressure. The remaining solid was washed with acetone and filtered to yield 258 grams (80 percent of theory) of 3t-butyl-4-neopentyl-l ,2-dithiolium hydrogen sulfate as a light yellow solid, m.p. 189190C; u.v.)t-H O max. (E) 254 mu (5,000) and 306 my. (6,800); nmr (solvent D 1 in ppm, internal standard t.m.s., 0.03 (s.,1H), 6.74 (s., 2H), 8.22 (s., 9H) and 8.88 (s., 911).

Anal. Calced, for C, H O S C, 44.14; 11,674;

S,29.43 Found: C, 43.98; l-l,6.82; S,29.8

EXAMPLE 2 3-t-Butyl-4-neopentyl-1,2dithiolium perchlorate (HSO; ClO To a solution of 5 grams of 3-tbutyl-4-neopentyl-l,Z-dithiolium hydrogen sulfate in 5 grams of distilled Water was added 4 cc of 70 percent perchloric acid. The white solid which precipitated was filtered and dried to yield 5 grams (100 percent) of material, m.p. 157158C; u.v. \EtOH max (E) 254 111,4 1,780 and 307 mu 5,010).

Anal. Calced. for C H S CIO; S, 19.5 Found: S, 19.4

EXAMPLE 3 3-t-Butyl-4-neopentyl-l,2-dithiolium hydrogen sulfate The product was prepared in 80 percent of the theoretical yield according to a procedure identical as in EXample 1, with the exception that instead of acetic acid as the solvent, a mixture of 50 g of acetic acid and 450 g of isopropanol as the solvent was employed.

EXAMPLE 4 3-t-Butyl-4-neopentyl-l,2-dithiolium hydrogen sulfate To a sample of 5.2 grams of 4-neopentyl-5-t-butyl 1,2-dithiole-3-thione dissolved in 100 grams of chloroform was added a solution of 12.2 grams of mchloroperbenzoic acid (85%) in 200 grams of chloroform. The mixture was allowed to stand for 24 hours at room temperature. The chloroform solution was evaporated under diminished pressure and the remaining solid extracted with 100 cc of distilled water. The aqueous solution was distilled under diminished pressure to yield 4.8 grams (73 percent of theory) of Ex. 1.

EXAMPLE? 4-Phenyl-l,2-dithiolium hydrogen sulfate This product was prepared in 80 percent yield from 4-phenyl 1,2-dithiole-3-thione according to the procedure described in Example 4. Bright yellow solid m.p. 230-232C. (dec.); u.v. A 11 0 max. (E) 242 my. (15,400) and 345 mp. (1,700), nmr (solvent D 0) in ppm, internal standard t.m.s., 0.06 (s., 2H) and 2.05-2.51 (m., 51-1).

Anal. Calced, for c,,H,o,s C, 39.1; H,2.9; S,34.8 Found: C, 38.8; H,3.1; S,34.9

EXAMPLE 6 3-(p-methoxy phenyl)-l,2thiolium hydrogen sulfate The desired product was obtained in a percent yield, according to the procedure described in Example 1, as an orange solid, m.p. 195-l96C. (dec.), after crystallization from ethanol; u.v.)t H O max. (E) 244 mp. (7,100) and 411 mu (23,300).

Anal. Calced. for C H O S C, 39.2; H,3.3; S,31.4

Found: C, 39.1; H,3.l; S,31.2 The formulae of the above dithiolium compounds are presented in the following Table:

TABLE II L La 4 Example R (3) R (4) X 1 (IJHa CH3 H50 CH3C- CH3- CH2 CH CH3 2 Same as above Same as above C104 3. .do ..do H804 do do H804 5 Q 6. H H804 CHaO- The reaction may be summarized as follows:

R .2 2 l 302 t $1 3=s H10 2 5 G g H HSO:

The anion employed will depend on the properties desired for example solubility, insolubility, partial solubility. Example of anions include sulfates, bisulfates, sulfites, bisulfites, halides, i.e. Cl, Br, 1, F, etc., phosphates, phosphites, etc., chlorates, etc. In addition to employing the salts, quaternaries can be employed so that the hydrogen in the 5 position R" is for example alkyl, aryl, etc.

Any suitable quaternizing agent may be employed, for example,

1. Alkyl halides such as methyl iodide, butyl iodide, butyl bromide, etc.

2. Sulfuric acid and derivatives H 50 R 80, where R is alkyl, etc., methyl, ethyl, etc. for example )z 4 3. Alkyl thioureas such as methyl thiourea, etc.

4. Sulfonate esters, for example where R is alkyl such as methyl, etc., and R is hydrogen, alkyl, etc. for example, methyl p-toluene sulfonates.

5. Alkyl phosphates, e.g. (MeO) PO, (EtO) PO, etc.

such as where X is sulfate, a dicarboxylic acid moiety such as from phthalic acid, etc. for example so t. S 4 9C Polyfunctional quaternaries may also be formed for example such as where A is alkylene,

CH CH OCH CH -CH -CI-I=CH-CH etc.

USE IN FLUIDS FOR DRILLING WELLS This phase of the invention relates to the use of the compounds of this invention as corrosion inhibitors in producing an improved drilling fluid useful in drilling oil and gas wells.

Fluids commonly used for the drilling of oil and gas wells are of two general types: water-base drilling fluids comprising, for example, a clay suspended in water, and oil-base drilling fluids comprising, for example, a clay or calcium carbonate suspended in mineral oil.

A third type of drilling fluid which has recently been developed, is one of oil-in-water or water-in-oil emulsion, for example, emulsions of mineral oil in water or Water in mineral oil formed by means of emulsifiers such as fulfuric acid; Turkey-red oil; soaps of fatty acids, for example, sodium oleate; emulsoid colloids,

for example, starch, sodium alginate, etc. Varying amounts of finely divided clay, silica, calcium carbon ate, blown asphalt and other materials may be added to these emulsions to improve their properties and control their weight.

I have now discovered that the compositions of this invention can be employed as a corrosion inhibitor in drilling fluids.

USE IN AIR DRILLING In has long been conventional practice in drilling deep bore holes to circulate a drilling mud down through the drill stem and up through the bore hole between the wall of the bore hole and the drill stem for the removal of chips or cuttings from the bore hole and to provide support for the wall of the bore hole. More recently, in the drilling of holes in which wall support provided by drilling mud is not employed, drilling has been carried out with the use of air for chip removal. Such drilling is not only normally faster than mud drilling but is indispensable in areas where the supply of water is limited or when drilling through cavernous formations into which the drilling mud flows and becomes lost.

The increasing popularity of air or gas drilling has come about not only because this method of drilling is frequently faster, as noted above, but for the additional reasons that the drill bits last longer, the provision and handling of water under wide ranges of temperature conditions is avoided, boring samples are easily observed when they are not mixed with mud, and there is no loss involved as in the case of mud drilling when drilling through cavernous formations. Furthermore, prompt removal of water entering the hole maintains a dry hole and the likelihood of wall collapse is thereby reduced.

In a typical air drilling operation there may be provided, for example, an up-flow of air in the bore hole having a velocity of the order of 3,000 feet per minute. This flow of air upwardly through the bore hole, which is produced by air pumped downwardly through the drill stem, provides adequate removal of cuttings. The air is delivered to the drill stem at pressures of 20 to 60 lbs. per square inch and for dewatering or for breaking obstructions, as will be hereinafter described, the pressures may be increased to to 200 lbs. or more per square inch. 3

Air drilling operations are frequently hampered by the inflow of water into the bore hole when the drill bit is penetrating a water bearing stratum or when the bore hole has passed through a water bearing stratum that has not been cased. Normally, if drilling proceeds uninterruptedly both before and during penetration into a water bearing stratum, the flow of air is sufficient to blow the water out of the bore hole along with the cuttings and drilling dirt. There are, however, two major problems encountered in air drilling when water is entering the bore hole. The first problem occurs when there is a small inflow of water sufficient to cause a dampening of the cuttings which, under certain conditions, will then ball-up, clogging and sometimes jamming the drill bit. The second problem is encountered when there is a substantial amount of water remaining in the bottom of, the bore hole during drilling causing a sloughing ofthe side wall of the bore hole. This latter condition may arise even though the water entering the bore hole is being blown out of the hole as fast as it enters. If there is a substantial inflow of water or if there is a substantial flow of water past a region of the bore hole susceptible to this condition, the water passing that region of the bore hole may cause a sloughing of the side wall.

The addition of foam-forming materials to the air flow when air drilling is employed in conjunction with sufficient water to provide foaming gives rise to numerous advantages in drilling operations. The water may be introduced either through a water bearing stratum being penetrated by the drill bitor, alternatively, if the hole is dry, water may be introduced from the surface of the earth through the drill stem in conjunction with the delivery of compressed air and foam forming material through the drill stem to the drill bit. In either case the water may be said to be existing in the bore hole, and drilling operations are described in US. Pat. No. 3,130,798.

The amount of the compositions of the invention to be employed as a corrosion inhibitor can vary widely depending upon particular compounds, the particular system, the amounts of oxygen present, etc. I may employ concentrations of from about 0.5 to 5,000 p.p.m., such as from about 4 to 4,000 p.p.m., for example from about to 2,000 p.p.m., but preferably from about 100 to 1,000 p.p.m. The optimum amount, to be determined in each instance, which will dependon function and economics, can be lesser or greater than the above amounts under proper conditions.

USE IN BRINES This phase of the invention relates to the prevention of corrosion in systems containing a corrosive aqueous medium, and most particularly in systems containing brines.

More particularly, this invention relates to the prevention of corrosion in the secondary recovery of petroleum by water flooding and in the disposal of waste water and brine from oil and gas wells. Still more particularly, this invention relates to a process of preventing corrosion in water flooding and in the disposal of waste water and brine from oil and gas wells which is characterized by injecting into an underground formation an aqueous solution containing minor amounts of compositions of this invention, in sufficient amounts to prevent the corrosion of metals employed in such operation. This invention also relates to corrosion inhibited brine solutions of these compounds.

When an oil well ceases to flow by the natural pressure in the formation and/or substantial quantities of oil can no longer be obtained by the usual pumping methods, various processes are sometimes used for the treatment of the oil-bearing formation in order to increase the flow of the oil. These processes are usually described as secondary recovery processes. One such process which is used quite frequently is the water flooding process wherein water is pumped under pressure into what is called an injection well and oil, along with quantities of water, that have been displaced from the formation, are pumped out of an adjacent well usually referred to as a producing well,. The oil which is pumped from the producing well is then separated from the water that has been pumped from the producing well and the water is pumped to a storage reservoir from which it can again be pumped into the injection well. Supplementary water from other sources may also be used in conjunction with the produced water. When the storage reservoir is open to the atmosphere and the oil is subject to aeration this type of water flooding system is referred to herein as an open water flooding system. If the water is recirculated in a closed system without substantial aeration, the secondary recovery method is referred to herein as a closed water flooding system.

Because of the corrosive nature of oil field brines, to economically produce oil by water flooding, it is necessary to prevent or reduce corrosion since corrosion increases the cost thereof. by making it necessary to repair and replace such equipment at frequent intervals.

I have now discovered a method of preventing corrosion in systems containing a corrosive aqueous media, and most particularly in systems containing brines, which is characterized by employing the compositions of this invention.

I have also discovered an improved process of protecting from corrosion metallic equipment employed in secondary oil recovery by water flooding such as injection wells, transmission lines, filters, meters, storage tanks, and other metallic implements employed therein and particularly those containing iron, steel, and ferrous alloys, such process being characterized by employing in water flood operation the compositions of this invention.

This phase of the invention then is particularly concerned with preventing corrosion in a water flooding process characterized by the flooding medium containing an aqueous or an oil field brine solution of these compounds.

In many oil fields large volumes of water are produced and must be disposed of where water flooding operations are not in use or where water flooding operations cannot handle the amount of produced water. Most States have laws restricting pollution of streams and land with produced waters, and oil producers must then find some method of disposing of the waste produced salt water. In many instances, therefore, the salt water is dosposed of by injecting the water into permeable low pressure strata below the fresh water level. The formation into which the water is injected is not the oil producing formation and this type of disposal is defined as salt water disposal or waste water disposal. The problems of corrosion of equipment are analogous to those encountered in the secondary recovery operation by water flooding.

The compositions of this invention can also be used in such water disposal wells thus providing a simple and economical method of solving the corrosion problems encountered in disposing of unwanted water.

Water flood and waste disposal operations are too well known to require further elaboration. In essence, in the present process, the flooding operation is effected in the conventional manner except that the flooding medium contains a minor amount of the compound of this invention, sufficient to prevent corrosion, in concentrations of about 10 p.p.m. to 10,000 p.p.m., or more, for example, about 50 to 5,000 p.p.m., but preferably about l5 to 1,500 ppm. The upper limiting amount of the compounds is determined by economic considerations. Since the success of a water flooding operation manifestly depends upon its total cost being less than the value of the additional oil recovered from the oil reservoir, it is quite important to use as little as possible of these compounds consistent with optimum corrosion inhibition. Optimum performance is generally obtained employing about 1,000 p.p.m. Since these compounds are themselves inexpensive and are used in low concentrations, they enhance the success of a flood operation by lowering the cost thereof.

In addition, these compounds are not sensitive to oxygen content of the water and these are effective corrosion inhibitors in both open water flooding systems and closed water flooding systems.

While the flooding medium employed in accordance with the present invention contains water or oil field brine and the compounds, the medium may also contain other materials. For example, the flooding medium may also contain other agents'such as surface active agents or detergents which aid in wetting throughout the system and also promote the desorption of residual oil from the formation, sequestering agents which pre vent the deposition of calcium and/or magnesium compounds in the interstices of the formation, bactericides which prevent the formation from becoming plugged through bacterial growth, tracers, etc. Similarly, they may be employed in conjunction with any of the operating techniques commonly employed in water flooding and water disposal processes, for example five spot flooding, peripheral flooding, etc., and in conjunction with other secondary recovery methods.

Corrosion tests were made using sand blasted 1020 mild steel coupons monitored by a polarization resistance meter, a PAIR instrument described in U.S. Pat. No. 3,406,101. These tests were made in cylindrical containers of 1,500 cc volume with provision for constant stirring by means of a motor driven impeller. A thermostatically controlled immersion heater maintained an average temperature of 75C. and an air inlet kept the fluids constantly saturated with air. Between each test the cylinder was cleaned with steam, benzene, acetone and thoroughly washed with clean' water. Results of these corrosion tests made in various aqueous environments are shown in the following Table.

Protection is calculated in the usual manner from corrosion rate (R of fluids without inhibitor and cor rosion rate (R in presence of particular inhibitor according to the formula (R R )/(R,) X 100 Percent protection.

4.2% NaCl, 1.7% MgCl 0.15% CaCl 0.09%

Na SO I Table 111 gives the values for continuous aerated hot (75C.) brines, having the above composition.

TABLE III Corrosion tests at 75C., in continuously aerated brine, corrosion rates in mpy. Blank rate 105 mpy, inhibitor concentrations 1,000 p.p.m.

use IN ACID SYSTEMS The compounds of this invention can also be employed as corrosion inhibitors for acid systems, for example as illustrated by the pickling of ferrous metals, the treatment of calcareous earth formations, etc., as described in the following sections.

USE AS PICKLING INHIBITORS This phase of the invention relates to pickling. More particularly, the invention is directed to a pickling composition and to a method of pickling ferrous metal. The term ferrous metal" as used herein refers to iron, iron alloys and steel.

To prepare ferrous metal sheet, strip, etc. for subsequent processing, it is frequently desirable to remove oxide coating, formed during manufacturing, from the surface. The presence of oxide coating, referred to as scale is objectionable when the material is to undergo subsequent processing. Thus, for example, oxide scale must be removed and a clean surface provided if satisfactory results are to be obtained from hot rolled sheet and strip in any operation involving deformation of the product. Similarly, steel prepared for drawing must possess a clean surface and removal of the oxide scale therefrom is essential since the scale tends to shorten drawing-die life as well as destroy the surface smoothness of the finished product. Oxide removal from sheet or strip is also necessary prior to coating operations to permit proper alloying or adherence of the coating to the ferrous metal strip or sheet. Prior to cold reduction, it is necessary that the oxide formed during hot rolling be completely removed to preclude surface irregularities and enable uniform reduction of the work' The chemical process used to remove oxide from metal surfaces is referred to as pickling. Typical pickling processes involve the use of aqueous acid solutions, usually inorganic acids, into which the metal article is immersed. The acid solution reacts with the oxides to form water and a salt of the acid. A common problem in this process is overpickling which is a condition resulting when the ferrous metal remains in the pickling solution after the oxide scale is removed from the surface and the pickling solution reacts with the ferrous base metal. An additional difficulty in pickling results from the liberated hydrogen being absorbed by the base metal and causing hydrogen embrittlement. To overcome the aforementioned problems in pickling, it has been customary to add corrosion inhibitors to the pickling solution.

The present invention avoids the above-described problems in pickling ferrous metal articles and provides a pickling composition vwhich minimizes corrosion, overpickling and hydrogen embrittlement. Thus the pickling inhibitors described herein not only prevent excessive dissolution of the ferrous base metal but effectively limit the amount of hydrogen absorption thereby during pickling. According to the invention, a pickling composition for ferrous metal is provided which comprises a pickling acid such as sulfuric or bydrochloric acid and a small but effective amount of the dithiol thione compound of this invention, for example at least about 5 p.p.m., such as from about to 5,000 p.p.m., but preferably for about 500 to 1,500 p.p.m.

Ferrous metal articles are pickled by contacting the surface (usually by immersion in the pickling solution) with a pickling composition as described to remove oxide from their surface with minimum dissolution and hydrogen embrittlement thereof and then washing the ferrous metal to remove the pickling composition therefrom.

USE IN ACIDIZING EARTH FORMATIONS The compositions of this invention can also be used as corrosion inhibitors in acidizing media employed in the treatment of deep wells to reverse the production of petroleum or gas therefrom and more particularly to an improved method of acidizing a calcareous or magnesium oil-bearing formation.

It is well known that production of petroleum or gas from a limestone, dolomite, or other calcareousmagnesian formation can be stimulated by introducing an acid into the producing well and forcing it into the oil or gas bearing formation. The treating acid, commonly a mineral acid such as HCl, is capable of forming water soluble salts upon contact with the formation and is effective to increase the permeability thereof and augment the flow of petroleum to the producing well.

USE AS CORROSION INHIBITORS IN HIGHLY ACID SYSTEMS TABLE IV H SO I80 g per liter Fe aS FeSO, 10 g per liter Fe"as Fe (SO 10 g per liter Inhibitor concentration I000 ppm Product of Time in Temperature Example No. Hrs Protection l 24 200 98 I 48 200 98 I 72 200 98 I 96 200 98 5 I 74 97 6 1 74 99 6 I7 74 99 TABLE V HCl I00 g per liter Fe as FcCl I00 g per liter Inhibitor concentration I000 ppm Product of Time in Temperature Example No. Hrs. F. Protection I 24 I75 96 I 48 I75 95 6 I 74 97 6 I8 74 98 An important aspect of pickling inhibitors is that they should remain effective in presence of dissolved ferrous ions (from dissolution of the oxide scale). The continued effectiveness of the present compositions is illustrated in the above table.

The compositions of this invention may also be added to other aqueous and/or oxygenated systems such as steam generating systems, water circulating systems such as in cooling towers, in automobile radiators, in diesel locomotive engines, in boiler water, sea-water ship ballast, etc.

The term dithiolium compounds" includes 1,2- dithiolium compounds and derivatives thereof such as salts, quaternaries, etc. I

The amount of l,2-dithiolium compound employe in treating the corrosive systems of this invention will vary with the particular compound employed, the-particular system, the solids present in the system, the degree of corrosivity of the system, etc. A minor amount of the compound is generally employed sufficient to impart corrosion protection to the system. In general one employs concentration of trace amounts such as from about 1.0 p.p.m. to 10,000 p.p.m., for example from 5 to 5,000 p.p.m. such as from to 2,500 p.p.m., but preferably from 500 to 2,000 ppm. In practice, concentrations of 1,000 i 200 p.p.m., are employed.

As is quite evident, new 1,2-dithiolium compounds will be constantly developed which could be useful in our invention. It is, therefore, not only impossible to attempt a comprehensive catalogue of such compositions, but to attempt to describe the invention in its broader aspects in terms of specific chemical names used would be too voluminous and unnecessary since one skilled in the art could by following the description of the invention herein select a useful dithioIe-thione compound. This invention lies in the use of suitable dithiolium compounds as corrosion inhibitors in aqueous and/or oxygenated and/or acid systems and their individual compositions are important only in the sense that their properties can affect this function. To precisely define each specific useful dithiolium compound and aqueous system in light of the present disclosure would merely call for knowledge within the skill of the art in a manner analogous to a mechanical engineer who prescribes in the construction of a machine the proper materials and the proper dimensions thereof. From the description in this specification and with the knowledge of a chemist, one will know or deduce with confidence the applicability of specific dithiolium compounds suitable for this invention by applying them in the process set forth herein. In analogy to the case of a machine, wherein the use of certain materials of construction or dimensions of part would lead to no practical useful result, various materials will be rejected as inapplicable where others would be operative. I can obviously assume that no one will wish to use a useless dithionium compound nor will be misled because it is wherein R and R are hydrogen, alkyl, aryl, cycloalkyl, alkenyl, alkynyl, alkaryl, aralkyl, or heterocyclic groups, or substituted groups thereof with the proviso that at least one ofR and R is not an aryl, alkaryl, aralkyl or substituted group thereof,

R is hydrogen, alkyl, aryl, cycloalkyl, alkenyl, alkynyl, alkaryl, aralkyl, or heterocyclic, or a substituted group thereof, X is a monofunctional anion, X is a polyfunctional anion, a is an integer, and 1 A is alkylene,

sac..-

2. The process of claim 1 where the corrosive medium is an aqueous brine system.

3. The process of claim 1 where the corrosive medium is an oil or gas well drilling fluid.

4. The process of claim 1 where the corrosive medium is an aqueous system in the presence of air.

5. The process of claim where the corrosive medium is an acid system.

6. The process of claim 5 where the acid system is an aqueous acid.

7. The process of claim 1 where the 1,2-dithiolium compound has the formula "til 15 i alkyl 8. The process of claim 7 where the corrosive medium is an aqueous brine system.

9. The process of claim 7 where the corrosive medium is an oil or gas well drilling fluid.

10. The process of claim 7 where the corrosive medium is an aqueous system in the presence of air.

11. The process of claim 7 where the corrosive medium is an acid system.

12. The process of claim 11 where the acid system is an aqueous acid.

13. The process of claim 7 where the 1,2-dithiolium compound has the formula V i s neoi entyl 14. The process of claim 13 where the corrosive medium is an aqueous brine system.

15. The process of claim 13 where the corrosive medium is an oil or gas well drilling fluid.

16. The process of claim 13 where the corrosive medium is an aqueous system in the presence of air.

17. The process of claim 13 where the corrosive medium is an acid system.

18. The process of claim 17 where the acid system is an aqueous acid. 

2. The process of claim 1 where the corrosive medium is an aqueous brine system.
 3. The process of claim 1 where the corrosive medium is an oil or gas well drilling fluid.
 4. The process of claim 1 where the corrosive medium is an aqueous system in the presence of air.
 5. The process of claim 1 where the corrosive medium is an acid system.
 6. The process of claim 5 where the acid system is an aqueous acid.
 7. The process of claim 1 where the 1,2-dithiolium compound has the formula
 8. The process of claim 7 where the corrosive medium is an aqueous brine system.
 9. The process of claim 7 where the corrosive medium is an oil or gas well drilling fluid.
 10. The process of claim 7 where the corrosive medium is an aqueous system in the presence of air.
 11. The process of claim 7 where the corrosive medium is an acid system.
 12. The process of claim 11 where the acid system is an aqueous acid.
 13. The process of claim 7 where the 1,2-dithiolium compound has the formula
 14. The process of claim 13 where the corrosive medium is an aqueous brine system.
 15. The process of claim 13 where the corrosive medium is an oil or gas well drilling fluid.
 16. The process of claim 13 where the corrosive medium is an aqueous system in the presence of air.
 17. The process of claim 13 where the corrosive medium is an acid system.
 18. The process of claim 17 where the acid system is an aqueous acid. 